arm-trusted-firmware

Pali Rohár 0ee80f35a2 fix(plat/marvell/a3720/uart): do external reset during initialization Sometimes when changing UART clock from TBG to XTAL, UART HW enters into some broken state. It does not transit characters from TX FIFO anymore and TX FIFO stays always empty. TX FIFO reset does not recover UART HW from this broken state. Experiments show that external reset can fix UART HW from this broken state. TF-A fatal error handler calls console_a3700_core_init() function to initialize UART HW. This handler may be called anytime during CPU runtime, also when kernel is running. U-Boot or Linux kernel may change UART clock to TBG to achieve higher baudrates. During initialization, console_a3700_core_init() resets UART configuration to default settings, which means that it also changes UART clock from TBG to XTAL. Do an external reset of UART via North Bridge Peripheral reset register to prevent this UART hangup. Signed-off-by: Pali Rohár <pali@kernel.org> Change-Id: I8990bce24d1a6fd8ccc47a2cd0a5ff932fcfcf14	3 years ago
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a3700_console.S	fix(plat/marvell/a3720/uart): do external reset during initialization	3 years ago

Pali Rohár 0ee80f35a2 fix(plat/marvell/a3720/uart): do external reset during initialization

Sometimes when changing UART clock from TBG to XTAL, UART HW enters into
some broken state. It does not transit characters from TX FIFO anymore
and TX FIFO stays always empty. TX FIFO reset does not recover UART HW
from this broken state.

Experiments show that external reset can fix UART HW from this broken
state.

TF-A fatal error handler calls console_a3700_core_init() function to
initialize UART HW. This handler may be called anytime during CPU
runtime, also when kernel is running.

U-Boot or Linux kernel may change UART clock to TBG to achieve higher
baudrates. During initialization, console_a3700_core_init() resets UART
configuration to default settings, which means that it also changes
UART clock from TBG to XTAL.

Do an external reset of UART via North Bridge Peripheral reset register
to prevent this UART hangup.

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I8990bce24d1a6fd8ccc47a2cd0a5ff932fcfcf14

3 years ago

a3700_console.S

fix(plat/marvell/a3720/uart): do external reset during initialization

3 years ago